Signaling by means of two complementary signals sent on two separate conductors, which is often referred to as differential signaling, is widely-used in modern high-frequency and high-speed digital and analog devices because of clearly-expressed advantages as compared to single-ended signaling. As for an example, differential signaling can considerably reduce noise in data transmission channels and radiation issues. Also, because differential and common modes (odd and even mode definition is also used in transmission line theory) are orthogonal ones, then both of these modes can be used in data transmission to increase capacity of the channels.
That is why, it is important to control a frequency response for the differential and common modes, or to provide separation of the differential and common modes, or suppressing one of these modes to make independent their receiving and transmitting.
From this viewpoint, differential-common mode filters are crucial components in analog and digital devices. Also it is important to make the filters as cost-effective components which can be easily integrated in a multifunctional system using in the devices.
U.S. Pat. No. 5,321,373 discloses a combined differential-mode common-mode filter. This filter has a plurality of U-shaped wires passing through a ferrite core.
U.S. Pat. No. 6,642,672 discloses an integrated filter with common-mode and differential-mode functions. This filter comprises a magnetic core, two windings and a frame for installing the windings.
US Patent Application Publication No. 2005/0063127A1 discloses a paired multi-layered dielectric independent passive component architecture resulting in differential and common mode filtering.
However, proposed common and differential mode filters do not provide selective separation of the differential and common modes in frequency domain and do not have a system to intensify a loss of the common mode, or the differential mode or both these modes in a predetermined frequency band.